Various problems are generally presented in treatment involving surgery to a patient's body. For example, the patient undergoing an operation must withstand the long hours of stress of the procedure. The surgeon, as well, is forced to endure intense concentration for the long period of operation. The danger of infection is always a possibility.
In order to lighten such various stress and to perform a necessary operation more safely and easily, various medical instruments such as catheters, guide wires and embolizing materials for occluding tubular organs such as vessels have recently been developed and been put to practical use.
With the recent advancement in medical instruments such as catheters and guide wires, an endovascular operation in which the intended diseased part is approached through a vessel is currently often performed in the treatment of diseases such as arteriovenous malformation, cerebral aneurysm and carotid-cavernous fistula.
At present time, releasable balloons, coils, liquid embolizing substances, particulate embolizing substances and the like are used as tubular organ embolizing materials. Once such an embolizing material is left or released at an erroneous or undesirable site in a tubular organ, however, it is generally next to impossible to recover it or to change the site.
Under such circumstances, proposals have heretofore been made for releasable embolizing materials, by which an embolizing material can be pulled back and reinserted even when one fails to deposit it at the intended site, and can be released and left after confirmation of the deposited site.
For example, Japanese Patent Application Laid-Open No. 500322/1993 (though PCT route) and Japanese Patent Application Laid-Open No. 265431/1995 proposed a method of leaving an embolizing material in, for example, an aneurysm, wherein the embolizing material such as a coil is provided at a distal end of a guide wire with a proper severable joint member, the embolizing material is placed at the intended site, and the joint member is then severed, thereby detaching the embolizing material from the guide wire to deposit it.
In order to detach the embolizing material in such a method, there is utilized a means of forming the joint member with a stainless steel and electrolyzing it by a positive current, thereby dissolving it, or a means of forming the joint member with polyvinyl alcohol and melting and severing it with a high-frequency current.
When an embolizing material is deposited at an affected part such as an aneurysm, it is generally conducted to first insert a microcatheter into the aneurysm and then send the embolizing material such as a coil by means of a wire for deposition through the microcatheter, thereby filling the embolizing material into the aneurysm. Two or more embolizing materials are successively inserted and deposited unless the aneurysm is fully filled with one embolizing material.
In the conventional medical implements for depositing implanted devices, however, embolizing materials to be inserted are those of specified lengths selected by expecting from various conditions. Therefore, in some cases, an embolizing material may actually not be completely inserted into an aneurysm since the aneurysm is filled up at a stage that the embolizing material is inserted halfway. In this case, it must be absolutely avoided to force the remainder of the embolizing material to insert into the aneurysm, since the cause of aneurysmal rupture is formed. On the other hand, when the remainder of the embolizing material is left in a vessel (parenteral artery) outside the aneurysm, the cause of thrombosis is formed. Therefore, it is necessary to pull back such an embolizing material to change it to an embolizing material of a proper length and to deposit the new embolizing material again.
However, when the embolizing material inserted halfway once is pulled back, the embolizing material may be entangled with an embolizing material already placed, or the coiled form of the embolizing material may be deformed. Further, both insertion and pulling out thereof may become impossible in some cases.